1. Field of the Invention
This invention relates to timing circuits, and more particularly to timing systems for training devices used to simulate mortar fire.
2. Description of the Related Art
Simulated mortar fire is employed in war games and other training exercises to provide a more realistic combat situation. The devices are fired from a launcher which operates by compressed air and calculates the desired trajectory and delay period until detonation, so that simulated explosions occur in the air over the trainees. The detonation produces a visual flash, an audible blast and smoke.
Detonation timers for other types of projectiles have typically been concerned with avoiding premature detonations to be sure the devices do not explode while still in the launcher. With simulated mortar fire, the problem has been found to be exactly the opposite. Whereas the launchers employed can typically withstand the force of a simulated mortar explosion, any unforeseen delay in the detonation can result in the projectile over-shooting its intended location and either exploding dangerously close to ground personnel, or actually striking someone.
No simulated mortar devices are available which have adequate safeguards against delayed detonation, or are selfchecking. Detonation timing systems designed for other applications, such as that disclosed in U.S. Pat. No. 4,644,864 to Komorowski et al., do not satisfy the needs of simulated mortar fire. Komorowski et al. is designed primarily for detonating a chaff-dispensing projectile for use in radar decoy operations. It employs a variable timing mechanism within the projectile that is inductively coupled with a control means in the launcher. A train of tone-burst modulated pulses are transmitted over the inductive coupling to the projectile, where the pulses are used to charge up a power storage capacitor. The pulses also set a counter in the projectile to the desired time delay between launching the projectile and its detonation to dispense the radar decoy chaff. The counter commences a counting-out operation at a predetermined rate in response to the projectile being launched, at the end of which operation the capacitor is discharged to initiate the detonation.
In addition to the requirements of having an accurate time setting device and avoiding the overshoot which results from too long a delay period before detonation, it would be very desirable to have a non-destructive technique for testing the operation of the timing system. At present, testing is accomplished by actually detonating a sampling of a production run, and projecting the results onto the entire run. This of course does not take individual variances into account, and is also wasteful.
In addition to accurate timing and a non-destructive test capability, the cost and size of simulated mortar projectiles should be as small as possible, with accompanying low power requirements.